Supported catalysts are of great economic significance and in quantitative terms represent the largest group of heterogeneous catalysts. They are used for example for processing fossil raw materials, in the further processing of intermediate products and in the synthesis of chemical products. In addition supported catalysts have gained significantly in economic significance in the field of exhaust gas cleaning for emission control.
In that respect titanium dioxide and titanium-bearing catalysts are a significant proportion. Commercially available catalyst carriers on a titanium dioxide basis are produced primarily by precipitation reactions of titanium-bearing salts, hydrolysis of titanium-bearing compounds or by flame pyrolysis of titanium-bearing precursors.
Supported catalysts play an important part in particular in the catalytic decomposition of nitrogen oxides. The occurrence of nitrogen oxides (NOx) in combustion processes is problematical from environmental points of view and various methods of reducing nitrogen oxides in exhaust gases are known. Selective catalytic reduction (SCR) has acquired particular significance, wherein the nitrogen oxides are reduced by added nitrogen-bearing compounds, preferably ammonia or urea, in the presence of a catalyst. Selective catalytic reduction of nitrogen oxides by means of ammonia (NH3—SCR) can be summarised as follows:

Sectors of use are in the static field for example power stations, coal-fired power stations, gas-fired power stations, refuse incineration installations, installations for nitric acid production or processing, steel works, and in the mobile field motor vehicles such as private cars and trucks as well as ships.
Commercial catalysts for SCR are in particular precious metals, metal oxides and zeolites. An overview is afforded by Pio Forzatti, Present status and perspectives in de-NOx SCR catalysis, in: Applied Catalysis A: General 222 (2001) 221-236. An important catalyst system is supported WO3— and V2O5—WO3-catalysts on a TiO2 support, wherein the TiO2 is usually predominately present in the anatase form (see for example U.S. Pat. No. 5,723,404 or WO 2006/044768).